This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
A pulse oximeter is a medical device that may be used to measure various blood characteristics such as oxygen saturation of hemoglobin in pulsing blood and/or a patient's pulse rate. To measure these characteristics, a non-invasive sensor may be used to pass light through a portion of blood perfused tissue (e.g., a finger, earlobe, or toe) and photo-electrically sense the absorption and scattering of light in the tissue. The amount of light absorbed and/or scattered is analyzed to estimate the amount of blood constituent in the tissue.
A detector signal resulting from measurement of the light absorbed and/or scattered by the blood perfused tissue includes information that describes the blood characteristics. As an example, pulses refer to the varying amount of arterial blood present in the tissue during a cardiac cycle. The varying amount of arterial blood yields cyclic attenuation of the light passing through the tissue. Accordingly, the detector signal from measurement of the light exhibits the familiar plethysmographic waveform representative of the cardiac cycle.
Analysis of detector signals involves processes that use various parameters. As an example, an analysis may involve filtering estimates of hemoglobin saturation to improve the accuracy of the saturation estimates. As another example, the analysis may involve filtering of plethysmographic waveforms. The filtering may use parameters such as filter weights or coefficients to adjust the filtering process. As another example, the analysis may involve applying pulse qualification criteria to qualify or disqualify pulses. The pulse qualification criteria may include parameters used to adjust the pulse qualification.
Under challenging conditions, it can be difficult to discern a valid arterial pulse from detector signals when using established pulse oximetery systems and methods. For example, under certain circumstances, pulse waveforms may be distorted by noise, which may make it difficult to discern a valid pulse among the distortions. Accordingly, it is desirable to provide a flexible and robust system and method for detecting valid arterial pulse signals when experiencing challenging conditions.